Year	Percent
1967	8
1968	8
1969	8
1970	6
1971	6
1972	6
1973	6
1974	6
1975	6
1976	6
1977	7
1978	9
1979	11
1980	11
1981	12
1982	12
1983	11
1984	11
1985	11
1986	11
1987	10
1988	10
1989	12
1990	12
1991	11
1992	8
1993	8
1994	14
1995	11
1996	12
1997	10
1998	17